US2010/0126534 discloses a pump including a housing, an impeller disposed in the pump housing, an electric motor for driving the impeller and a heating device for heating washing liquid in the pump housing. The housing of the pump includes a housing base and a housing cover. The heating device is mounted between the housing base and the housing cover and forms a ring-shaped side wall of the housing. The washing liquid is heated only by the inner surface of the heating device after it flows out of the impeller.